1. Field of the Invention
The present invention relates generally to dental implants and, more particularly, to a threaded implant body with a pre-attached healing cap that can be quickly and safely placed into the jaw as a single unit.
2. Background of the Related Art
Dental implants are placed in the jaw to provide support for a dental restoration, fixed bridge or removable partial denture. Dental implants provide good chewing function and also improve the patient's cosmetic appearance thereby allowing the patient to smile, speak, and interact with others with greater confidence.
One type of dental implant widely used in the industry is typically referred to as a "threaded" implant. Threaded implants have an externally threaded body portion which is screwed into a pre-drilled hole (i.e. an osteotomy) in the patient's upper or lower jawbone. Typically, the threaded implant body is formed with a central threaded socket accessible through the overlying gum tissue for receiving and supporting one or more dental attachments or components. Types of attachments and components that are received by the central socket include healing caps, impression copings and abutments. In turn, some of these attachments and components are useful to fabricate and/or support the prosthodontic restoration.
Dental implants are typically packaged as an assembly including all the tools necessary for the insertion of the implant into an osteotomy formed in the jaw. A typical threaded implant assembly includes a threaded implant body, an implant carrier, an insertion post, a coupling screw and a healing cap. The implant carrier, insertion post, and coupling screw are tools which are used during the insertion of the implant body. Typically, the implant carrier, insertion post and coupling screw are discarded after the implant body has been inserted into the osteotomy. The healing cap seals and protects the central socket of the implant body during the initial healing period.
During the insertion of a conventional threaded implant, the insertion post is mechanically coupled to the top of the implant body by a coupling screw which traverses a central through-cavity in the insertion post and is threaded into the central threaded socket in the implant body. Typically, the bottom end of the insertion post is formed with a hexagonal cavity that irrationally mates with a corresponding hexagonal protrusion formed on the top of the implant body thereby preventing any relative rotation between the insertion post and implant body while coupled.
An implant carrier is releasably coupled to the top of the insertion post and provides the dental practitioner with a means to grip and manipulate the assembly during the initial implantation procedure. Typically, the implant carrier is formed with a generally hexagonal internal passage at its bottom end which mates with a generally hexagonal outer surface near the top of the insertion post. The dental practitioner uses the implant carrier to manipulate the implant body into the proper location within the jawbone. Torque is applied to the implant carrier which is transferred, via the insertion post, to the threaded implant body.
In use, the first step of a typical implantation procedure involves making an incision in the patient's gum tissue. A portion of the gum tissue is then folded back and an osteotomy is drilled in the jawbone. The diameter of the osteotomy is equal to or slightly smaller than the diameter of the implant body. The implant carrier is then used to transport the threaded implant assembly to the surgical site. The implant carrier is gripped by the practitioner and is used to manipulate the implant body into the correct position and then to partially screw the threaded implant body into the osteotomy.
Once the implant body has been initially placed in the osteotomy and tightened manually, the implant carrier is decoupled from the insertion post and is removed from the surgical site. If necessary, a suitable wrench or dental hand piece is then used to engage the insertion post and drive the implant to its final depth within the osteotomy. The coupling screw is then removed and the insertion post is decoupled from the implant body leaving only the implant body in the patient's mouth.
The healing cap is housed in a cavity formed in the top of the implant carrier where it is contained by a paper barrier until needed. At this point, the healing cap is removed from the implant carrier and is threaded into the central socket of the implant body. Typically, a tool with a hexagonal tip is inserted into a corresponding mating hexagonal recess located in the top center of the healing cap and is used to apply torque to tighten the healing cap. The healing cap protects the implant socket against bone or tissue in growth during the initial healing period, and also prevents the entry of bacteria or other contaminants into the central socket of the implant body.
The insertion of the implant body and healing cap is then followed by an initial healing period in which the bone is allowed to surround and retain the implant (i.e. "osseointegrate" with the implant) and the gum tissue is allowed to heal over the implant body and healing cap. For implants placed in the mandible, healing typically requires about three months; for implants in the maxilla, the healing period typically requires about six months.
After the implant body has sufficiently osseointegrated with the jawbone, the gum tissue is re-opened by making an incision and the gum tissue is folded back to expose the healing cap. The hexagonal tool is inserted into the recess in the top of the healing cap and torque is applied to rotate the healing cap out of the implant socket and to remove it from the implant body. During this step of the procedure, great care must be used to remove the healing cap without disturbing the position of the implant body. Any disturbance of the implant body during the removal of the healing cap could damage the osseointegration between the implant body and the jawbone. Damage to the osseointegration is very undesirable and could endanger the entire restoration process by destabilizing the implant. In addition, any movement of the implant body could result in gaps or spaces between the implant body and jawbone which could in turn lead to infection by bacteria and/or other contaminants
After the healing cap has been unscrewed and removed from the patient's mouth, a suitable healing abutment is inserted into the central socket. The healing abutment extends through the gum tissue overlying the implant site. A second healing period then ensues in which the gum tissue is allowed to heal around the post-osseointegration healing abutment. Typically, this second healing period lasts from four to eight weeks.
After the second healing period has ended, the healing abutment is removed from the implant body. Typically, an impression is taken of the patient's mouth to fabricate a prosthesis or dental restoration. An abutment supporting the final restoration is then attached to the implant body. Lastly, the restoration is cemented or screwed to the abutment and/or implant body to complete the placement of the prosthodontic restoration in the patient's mouth.
The conventional threaded dental implant described above is commonly used by dental practitioners and is preferred for its ability to achieve a good mechanical connection between the implant body and the jawbone. However, this type of threaded implant suffers from several significant shortcomings. In particular, the insertion of a conventional threaded dental implant is a difficult and time consuming procedure. The procedure is difficult because, after the implant body has been inserted in the osteotomy, the coupling screw holding the insertion post to the implant body must be removed very carefully such that the position of the implant body is not affected. Any movement of the implant body is undesirable because precise placement of the implant body is critical to the success of the implant procedure. Similarly, the attachment of the healing cap must also be performed with great care. If the healing cap is not tightened sufficiently, the patient runs the risk of infection in the gap between the implant body and the healing cap or in the implant socket. On the other hand, if too much torque is applied, it may be difficult or impossible to remove the healing cap after the healing period without affecting the position of the implant body or damaging the osseointegration between the implant body and the jawbone.
The procedure for inserting a conventional threaded dental implant is time consuming because of the numerous steps involved in the procedure. After inserting the implant body, the dental practitioner must first remove both the insertion post and coupling screw from the implant body and then insert and tighten the healing cap to cover the exposed socket. Each of these steps can be very cumbersome and allows for the possibility of human error. Additionally, there is the possibility that the insertion post, coupling screw and the healing cap, which are generally small in size, may inadvertently be lost in the patient's mouth during the implantation procedure.
The above shortcomings were addressed in a threaded dental implant design disclosed in U.S. Pat. No. 5,755,575 to Biggs. In Biggs, the healing cap is attached to the implant body before the implant body is inserted into the patient's mouth to reduce the overall number of steps required in the dental restoration procedure. In Biggs, the healing cap is also used as a driver to screw the implant body into the osteotomy. Although Biggs reduces the number of steps involved in the implantation procedure, Biggs suffers from a further shortcoming because the healing cap has no threads and is press-fitted into the implant socket. As a result, there is no tension force pulling the healing cap down against the top of the implant body. Without any tension, there is no assurance that the healing cap will be touching the implant body and a gap may result between the healing cap and implant body. Any gap between the healing cap and the implant body is disadvantageous because it could lead to infection by bacteria or other contaminants. Therefore, Biggs does not provide sufficient protection against infection.
Another type of dental implant widely used in the industry is typically referred to as a "cylindrical" implant. Cylindrical implants have also been designed wherein the healing cap is pre-attached to the implant body to simplify the implantation procedure. However, cylindrical implants are not suitable in all situations and do not provide desired initial stability within the jawbone as provided by a threaded implant.
Thus, there exists a need for an improved threaded dental implant in which the healing cap is pre-attached to the implant body such that both the implant body and healing cap can be inserted simultaneously into the patient's mouth in a simple one-step procedure. It is also desirable that such a pre-attached healing cap be pulled down against the implant body thereby sealing off the implant socket and minimizing the risk of infection during the healing period.